Synthetic plastic laminates, particularly such as glass fibre reinforced resin laminate, are in wide, use, and are popular for their features of moldability, appearance, weather resistance, strength, and light weight. It is well known, however, that such laminates require special care in the attachment of any fastening devices such as bolts, rivets, and the like. If, for example, it is attempted to secure an article to such a laminate by simply drilling a hole through the laminate and bolting the article to the laminate, it is well known that stress is applied by the bolt to the laminate, and the laminate will sooner or later break down around the hole, and the bolt will become detached from the laminate.
The reason is that while the glass fibres have excellent properties in resisting stresses applied along their length, they have very little capacity for resisting stresses applied transversely. The forces applied by the bolt or other fastening devices may, in same cases, simply be compressive forces, and may also apply forces resulting from the attachment of some article by means of the bolt to the laminate, and it is these forces which cause the laminate to break down around the location of the hole.
In order to overcome this problem, it has been the practice in the past to attempt to increase the thickness of the laminate inthe region where the article is to be bolted. This may be done by simply increasing the layers of laminate in that area. This procedure is somewhat time consuming and troublesome, and while the increased thickness of the layers of laminate may somewhat prolong the life of the laminate, the basic problem still exists, namely that the glass fibres have very little capacity for resisting stresses applied transversely to their length.
Alternatively, the laminate may incorporate some piece of material, in the region where the hole is to be drilled. Such material is usually selected from materials such as metal, wood, and the like, so as to withstand the local stresses imposed by the bolt. This solution is not, however, free from problems. The bond between the laminate and the reinforcement is simply an adhesive bond, and is likely to sooner or later break down with the result that the reinforcement becomes loose within the laminate. It then no longer acts as a reinforcement, and the laminate will soon be damaged by the bolt.